Formation and structural characterization of a europium(II) mono(scorpionate) complex and a sterically crowded pyraza-bole

Abstract

The reaction of EuI₂(THF)₂ with potassium hydro-tris-(3,5-diiso-propyl-pyrazol-yl)borate (K[HB(3,5- ^iPr2pz)₃] (= KTp ^iPr2, pz = pyrazol-yl) in a molar ratio of 1:1.5 resulted in extensive ligand fragmentation and formation of the europium(II) mono(scorpionate) complex bis-(3,5-diisopropyl-1H-pyrazole)[hydro-tris-(3,5-diiso-propyl-pyrazol-yl)borato]iodido-europium(II), [Eu(C₂₇H₄₆BN₆)I(C₉H₁₆N₂)₂] or (Tp ^iPr2)(3,5- ^iPr2pzH)₂Eu^III, 1, in high yield (78%). As a typical by-product, small amounts of the sterically crowded pyraza-bole derivative trans-4,8-bis-(3,5-diiso-propyl-pyrazol-1-yl)-1,3,5,7-tetra-iso-propyl-pyraza-bole, C₃₆H₆₂B₂H₈ or trans-{(3,5- ^iPr2pz)HB(μ-3,5- ^iPr2pz)}₂, 2, were formed. Both title compounds have been structurally characterized through single-crystal X-ray diffraction. In 1, two isopropyl groups are each disordered over two orientations with occupancy ratios of 0.574 (10):0.426 (10) and 0.719 (16):0.281 (16). In 2, one isopropyl group is similarly disordered, occupancy ratio 0.649 (9):0.351 (9).

Keywords: crystal structure; europium; pyraza­bole; pyrazolylborate; scorpionate.